Web design and programming Lecturer: Ahmed Ali Saihood

1. Subject: Web Design and Programming Lecturer: Ahmed Ali Saihood
1
Chapter 5
Part II
PHP
PHP if...else...elseif Statements:
Conditional statements are used to perform different actions based on
different conditions.
In PHP we have the following conditional statements:
 if statement - executes some code if one condition is true
 if...else statement - executes some code if a condition is true and
another code if that condition is false
 if...elseif....else statement - executes different codes for more
than two conditions
 switch statement - selects one of many blocks of code to be
executed
1. PHP - The if Statement
The if statement executes some code if one condition is true.
Syntax
if (condition) {
code to be executed if condition is true;
}

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The example below will output "Have a good day!" if the current time
(HOUR) is less than 20:
Example
<?php
$t = date("H");
if ($t < "20") {
echo "Have a good day!";
}
?>
2. PHP - The if...else Statement
The if....else statement executes some code if a condition is true and
another code if that condition is false.
Syntax
if (condition) {
code to be executed if condition is true;
} else {
code to be executed if condition is false;
}
The example below will output "Have a good day!" if the current time is
less than 20, and "Have a good night!" otherwise:
Example
<?php
$t = date("H");
if ($t < "20") {
echo "Have a good day!";

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} else {
echo "Have a good night!";
}
?>
3. PHP - The if...elseif....else Statement
The if....elseif...else statement executes different codes for more than
two conditions.
Syntax
if (condition) {
code to be executed if this condition is true;
} elseif (condition) {
code to be executed if this condition is true;
} else {
code to be executed if all conditions are false;
}
The example below will output "Have a good morning!" if the current
time is less than 10, and "Have a good day!" if the current time is less
than 20. Otherwise it will output "Have a good night!":
Example
<?php
$t = date("H");
if ($t < "10") {
echo "Have a good morning!";
} elseif ($t < "20") {
echo "Have a good day!";
} else {

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echo "Have a good night!";
}
?>
4. The PHP switch Statement
Use the switch statement to select one of many blocks of code to be
executed.
Syntax
switch (n) {
case label1:
code to be executed if n=label1;
break;
case label2:
code to be executed if n=label2;
break;
case label3:
code to be executed if n=label3;
break;
...
default:
code to be executed if n is different from all
labels;
}
This is how it works: First we have a single expression n (most often a variable),
that is evaluated once. The value of the expression is then compared with the
values for each case in the structure. If there is a match, the block of code
associated with that case is executed. Use break to prevent the code from running
into the next case automatically. The default statement is used if no match is
found.
Example
<?php
$favcolor = "red";

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switch ($favcolor) {
case "red":
echo "Your favorite color is red!";
break;
case "blue":
echo "Your favorite color is blue!";
break;
case "green":
echo "Your favorite color is green!";
break;
default:
echo "Your favorite color is neither red, blue, nor
green!";
}
?>
5.PHP while Loops
The while loop executes a block of code as long as the specified
condition is true.
Syntax
while (condition is true) {
code to be executed;
}
The example below first sets a variable $x to 1 ($x = 1). Then, the while
loop will continue to run as long as $x is less than, or equal to 5 ($x <=
5). $x will increase by 1 each time the loop runs ($x++):
Example
<?php
$x = 1;

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while($x <= 5) {
echo "The number is: $x <br>";
$x++;
}
?>
6. The PHP do...while Loop
The do...while loop will always execute the block of code once, it will
then check the condition, and repeat the loop while the specified
condition is true.
Syntax
do {
code to be executed;
} while (condition is true);
The example below first sets a variable $x to 1 ($x = 1). Then, the do
while loop will write some output, and then increment the variable $x
with 1. Then the condition is checked (is $x less than, or equal to 5?),
and the loop will continue to run as long as $x is less than, or equal to 5:
Example
<?php
$x = 1;
do {

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echo "The number is: $x <br>";
$x++;
} while ($x <= 5);
?>
7. The PHP for Loop
The for loop is used when you know in advance how many times the
script should run.
Syntax
for (init counter; test counter; increment counter) {
code to be executed;
}
Parameters:
•init counter: Initialize the loop counter value
•test counter: Evaluated for each loop iteration. If it evaluates to TRUE,
the loop continues. If it evaluates to FALSE, the loop ends.
•increment counter: Increases the loop counter value
The example below displays the numbers from 0 to 10:
Example
<?php
for ($x = 0; $x <= 10; $x++) {
echo "The number is: $x <br>";

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}
?>
8. The PHP foreach Loop
The foreach loop works only on arrays, and is used to loop through each
key/value pair in an array.
Syntax
foreach ($array as $value) {
code to be executed;
}
For every loop iteration, the value of the current array element is
assigned to $value and the array pointer is moved by one, until it reaches
the last array element.
The following example demonstrates a loop that will output the values
of the given array ($colors):
Example
<?php
$colors = array("red", "green", "blue", "yellow");
foreach ($colors as $value) {
echo "$value <br>";
}
?>